A Transmission Active Lubrication Control Method Based on Oil Film Thickness

Abstract

The present invention discloses a method for actively lubricating and controlling a transmission based on oil film thickness, comprising the following steps: S1: Reading information on vehicle speed, transmission input torque, and initial transmission temperature; S2: Calculating the theoretical value of the minimum oil film thickness under different working conditions; and determining the empirical value of the minimum oil film thickness; S3: Determining the lubricating oil temperature T i and the dynamic target optimized temperature T0 at different vehicle speeds; S4: Comparing the lubricating oil temperature T i at the current vehicle speed with the dynamic target optimized temperature T0. If the lubricating oil temperature T i is greater than the dynamic target optimized temperature T0, the active lubrication control system cools the lubricating oil; otherwise, the active lubrication system is turned off; S5: Judging whether the change rate of the difference between the lubricating oil temperature T i and the dynamic target optimized temperature T0 is less than a threshold value. If the change rate is greater than or equal to the threshold value, adjust the lubricating oil flow rate and the rotational speed of the cooling fan; otherwise, the active lubrication system stops working. The present invention can effectively control the working temperature of the transmission, improving the working reliability and service life of the transmission.

Description

Technical Field

[0001] The present invention relates to the technical field of transmissions, and particularly to an active lubrication control method for a transmission based on oil film thickness. Background Art

[0002] As an important part of the transmission system, the transmission can reduce the rotational speed and increase the torque. However, with the continuous increase of the limit rotational speed of the power source, higher requirements are put forward for the lubrication performance of the transmission, and the lubrication and cooling problems of the transmission cannot be ignored.

[0003] Currently, splash lubrication is commonly used in transmissions, which is a passive gear lubrication and cooling method. The heat dissipation capacity of the transmission under this lubrication method is limited, and the transmission oil temperature is likely to be too high under high rotational speed and high torque conditions, resulting in a decrease in the viscosity of the lubricating oil, a decrease in the oil film thickness in the local area of the gear meshing tooth surface, and mixed lubrication, resulting in tooth surface scuffing or even fatigue fracture.

[0004] In order to achieve good heat dissipation effect of the transmission, if direct large-flow injection lubrication is carried out to minimize the transmission temperature, it will cause an increase in the viscosity of the lubricating oil, an increase in the heat generated by gear meshing, bearing friction, and gear churning loss during the operation of the transmission, and a sharp increase in the energy consumption of the entire system. Therefore, there is an urgent need for a lubrication control method that can comprehensively consider the influencing factors of the transmission operation and select an accurate target optimized temperature. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides an active lubrication control method for a transmission based on oil film thickness, which fully considers the factor that the oil film thickness of the gear meshing tooth surface decreases due to too high oil temperature under some harsh working conditions of the transmission. This control method can effectively control the working temperature of the transmission and improve the working reliability and service life of the transmission.

[0006] In order to achieve the above object, the present invention provides an active lubrication control method for a transmission based on oil film thickness, including the following steps:

[0007] S1: Read the vehicle speed, transmission input torque, and transmission initial temperature information;

[0008] S2: Divide different working conditions according to different vehicle speeds, transmission input torques, and transmission initial temperatures, and calculate the oil film thickness under different working conditions; according to the elastohydrodynamic lubrication theory, determine the empirical value of the minimum oil film thickness;

[0009] S3: Determine the lubricating oil temperature T corresponding to the vehicle speed according to the oil film thickness at different vehicle speeds obtained in step S2 i; Determine the dynamic target optimization temperature T0 corresponding to the vehicle speed according to the empirical value of the minimum oil film thickness determined in step S2;

[0010] S4: Compare the lubricating oil temperature T at the current vehicle speed i with the dynamic target optimization temperature T0. If the lubricating oil temperature T i is greater than the dynamic target optimization temperature T0, then increase the radiator pump flow rate and the fan speed; if the lubricating oil temperature T i is less than or equal to the dynamic target optimization temperature T0, the active lubrication system is turned off;

[0011] S5: Determine whether the rate of change of the difference between the lubricating oil temperature T i and the dynamic target optimization temperature T0 is less than the threshold value. If the rate of change of the difference is greater than or equal to the threshold value, adjust the lubrication flow rate and the cooling fan speed in a timely manner. If the rate of change of the difference is less than the threshold value or the vehicle stops, the active lubrication system stops working.

[0012] Further, a method for active lubrication control of a transmission based on the oil film thickness is characterized in that: in the step S2, the calculation formula for the film thickness of elastohydrodynamic lubrication is:

[0013]

[0014] where h(x) is the oil film thickness; h0 is the clearance between two contacting rigid bodies; x is the horizontal coordinate; R is the equivalent curvature radius; v(x) is the elastic displacement of each point on the contact surface in the vertical direction.

[0015] Further, in the step S2, according to the elastohydrodynamic lubrication theory, when the fluid film becomes thinner than 0.1 μm, that is, it starts to enter the mixed lubrication state, the empirical value of the minimum oil film thickness is determined to be 0.1 μm, and the transmission lubricating oil temperature corresponding to the empirical value of the minimum oil film thickness is the safe operating temperature.

[0016] Further, in the step S5, the threshold value of the rate of change of the difference between the lubricating oil temperature T i and the dynamic target optimization temperature T0 is 1%.

[0017] The beneficial effects of the present invention:

[0018] Based on the elastohydrodynamic lubrication theory and the viscosity-temperature characteristics of the lubricating oil, the present invention analyzes the oil film thickness of the meshing tooth surfaces under different working conditions, determines the dynamic target optimization temperature scheme, and thus proposes a method for active lubrication control of a transmission based on the oil film thickness. This method fully considers the factor that the oil film thickness of the gear meshing tooth surfaces decreases due to too high oil temperature under some harsh working conditions of the transmission, can effectively control the working temperature of the transmission, and improves the working reliability and service life of the transmission. Description of the Drawings

[0019] Figure 1 It is a flow chart of an active lubrication control method for a transmission based on oil film thickness according to the present invention.

[0020] Figure 2 It is a comparison chart of the results of an active lubrication control method for a transmission based on oil film thickness according to the present invention.

[0021] Figure 3 It is a line contact elastohydrodynamic lubrication model based on oil film thickness according to the present invention.

[0022] Figure 4 It is a diagram showing the variation of oil film thickness with the initial temperature in the present invention. Specific embodiments

[0023] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0024] The present invention discloses an active lubrication control method for a transmission based on oil film thickness.

[0025] Referring to Figure 1 , an active lubrication control method for a transmission based on oil film thickness includes the following steps:

[0026] S1: Use a vehicle speed sensor to read the vehicle speed information, calculate the torque information of the transmission at the current vehicle speed, and use a temperature sensor to read the initial temperature information of the transmission.

[0027] Among them, the calculation of the total vehicle driving force of the vehicle is as follows:

[0028]

[0029] Among them, F out is the total vehicle driving force; m is the total vehicle mass; g is the acceleration due to gravity; f is the rolling resistance coefficient; α1 is the ramp angle; δ is the conversion coefficient of the rotating mass; a is the vehicle acceleration; C D is the air resistance coefficient; A is the vehicle frontal area; v is the driving speed.

[0030] The calculation of the transmission input torque is as follows:

[0031]

[0032] T in is the transmission input torque; i0 is the total transmission ratio of the two-stage transmission; i g is the transmission ratio of the main transmission or the wheel-side transmission; ηT is the mechanical transmission efficiency.

[0033] S2: Use SolidWorks and Romax to establish the transmission housing model and the transmission gear pair model respectively, and import the transmission housing model into Romax to couple it with the transmission gear pair model; in the Romax software, divide different working conditions according to different vehicle speeds, transmission input torques, and initial transmission temperatures, and through the simulation calculations of the above three parameters, obtain the oil film thicknesses under different working conditions; according to the elastohydrodynamic lubrication theory, when the fluid film thins to less than 0.1 μm, it begins to enter the mixed lubrication state, and the empirical value of the minimum oil film thickness is determined to be 0.1 μm, which can ensure lubrication reliability.

[0034] Among them, referring to Figure 3 , the calculation formula for the film thickness of line contact elastohydrodynamic lubrication is:

[0035]

[0036] Among them, h(x) is the oil film thickness; h0 is the clearance between two contacting rigid bodies; x is the horizontal coordinate; R is the equivalent curvature radius; v(x) is the elastic displacement of each point on the contact surface in the vertical direction, and the equation is:

[0037]

[0038] Among them, s is the additional coordinate on the x-axis, representing the distance between any line load p(s)ds and the origin of coordinates; p(s) is the load distribution function; c is a constant to be determined; x in and x out are the starting and ending coordinates of the load p(s), and the equation is:

[0039]

[0040] Among them, b is the half-width of Hertz contact.

[0041] S3: According to the oil film thicknesses at different vehicle speeds obtained in step S2, determine the lubricating oil temperature T i . To ensure that the transmission gears do not undergo mixed lubrication, use the safe operating temperatures at different vehicle speeds as the target optimization temperature T0; and the safe operating temperatures of the lubricating oil at different vehicle speeds are obtained through simulation calculations based on the empirical value of the minimum oil film thickness of 0.1 μm in step S2 and input into the transmission motion model in Romax.

[0042] S4: Compare the current lubricating oil temperature T i with the dynamic target optimization temperature T0 at the corresponding vehicle speed. If the lubricating oil temperature T i is greater than the dynamic target optimization temperature T0, then increase the radiator pump flow rate and the fan speed. If the lubricating oil temperature Ti If it is less than or equal to the dynamic target optimization temperature T0, the active lubrication system is turned off. This method can effectively increase the heat exchange rate between the lubricating oil and the air, reduce the temperature of the lubricating oil, and improve the reliability of the transmission operation.

[0043] S5: Determine the lubricating oil temperature T i Whether the change rate of the difference from the dynamic target optimization temperature T0 is less than the threshold value. After multiple experimental analyses, the threshold value of the change rate of the difference between the lubricating oil temperature T i and the dynamic target optimization temperature T0 is 1%, which can effectively control the working temperature of the transmission, ensure the reliable operation of the transmission and reduce the calculation cost. If the change rate of the difference between the lubricating oil temperature T i and the dynamic target optimization temperature T0 is greater than or equal to 1%, the lubrication flow rate and the rotation speed of the cooling fan are adjusted timely. If the change rate is less than the threshold value or the vehicle stops, the active lubrication system stops working. Refer to Figure 2 , (a) shows the oil temperature of the splash lubrication transmission and the dynamic target optimization oil temperature, and (b) shows the oil temperature of the active lubrication transmission and the dynamic target optimization oil temperature.

[0044] Inspired by the ideal embodiments of the present invention described above, through the above description, relevant staff can completely make various changes and modifications without departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A method for controlling active lubrication of a transmission based on oil film thickness, characterized in that: It includes the following steps: S1: Read the information of vehicle speed, transmission input torque and initial transmission temperature; S2: Divide different working conditions according to different vehicle speeds, transmission input torques and initial transmission temperatures, and calculate the oil film thickness under different working conditions; According to the elastohydrodynamic lubrication theory, determine the empirical value of the minimum oil film thickness; S3: Determine the lubricating oil temperature T corresponding to the vehicle speed based on the oil film thicknesses at different vehicle speeds obtained in step S2. i Determine the dynamic target optimization temperature T0 corresponding to the vehicle speed according to the empirical value of the minimum oil film thickness determined in step S2. S4: Compare the lubricating oil temperature T at the current vehicle speed i with the dynamic target optimized temperature T0. If the lubricating oil temperature T i is greater than the dynamic target optimized temperature T0, increase the radiator pump flow rate and the fan speed; if the lubricating oil temperature T i is less than or equal to the dynamic target optimized temperature T0, the active lubrication system is turned off; S5: Determine the lubricating oil temperature T i Whether the change rate of the difference from the dynamic target optimized temperature T0 is less than the threshold value. If the change rate of the difference is greater than or equal to the threshold value, adjust the lubricating flow rate and the rotational speed of the cooling fan in a timely manner. If the change rate of the difference is less than the threshold value or the vehicle stops, the active lubrication system stops working; In the step S2, the calculation formula for the film thickness of elastohydrodynamic lubrication is as follows: Among them, h(x) is the oil film thickness; h0 is the clearance between two contacting rigid bodies; x is the horizontal coordinate; R is the equivalent curvature radius; v(x) is the elastic displacement of each point on the contact surface in the vertical direction; In the step S2, according to the elastohydrodynamic lubrication theory, when the fluid film becomes thinner and less than 0.1μm, it starts to enter the mixed lubrication state, and the empirical value of the minimum oil film thickness is determined to be 0.1μm, and the transmission lubricating oil temperature corresponding to the empirical value of the minimum oil film thickness is the safe operating temperature.

2. The active lubrication control method for a transmission based on oil film thickness according to claim 1, characterized in that: In the step S5, the temperature T of the lubricating oil i The threshold of the rate of change of the difference between the dynamic target optimized temperature T0 is 1%.

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